1. Field of the Invention
The present invention relates to rolling of sheet metal strip in a rolling mill having roll crossing and bending systems for effecting strip profile and flatness and to a method for controlling the rolling mill. A series of hot and cold rolling mills having such systems and controls are used for obtaining desired thickness, profile and flatness for finished metal strip.
2. Description of Related Art
In the production of finished metal strip by hot and cold rolling operations it is advantageous to control the process so as to produce finished strip having a strip thickness, profile and flatness acceptable to the end user. During rolling, strip profile is controlled by varying the shape of the gap between work rolls of a rolling mill which is referred to as the roll gap profile. Such roll gap profile control can be carried out on mills having solely work rolls (2-high), work rolls with back-up rolls (4-high), work rolls with intermediate rolls followed by back-up rolls (6-high), or work rolls with multiple back up and/or intermediate rolls. Other variations wherein the number of top rolls differ from the number of bottom rolls are also possible. The roll gap profile can be controlled by means such as using non-cylindrically shaped rolls, roll axial shifting in combination with non-cylindrically shaped rolls, roll heating or cooling, roll bending, roll crossing and combinations of such methods.
U.S. Pat. No. 1,860,931 describes a 4-high rolling mill having roll crossing of solely back-up rolls.
U.S. Pat. No. 4,453,393 describes a 4-high rolling mill wherein work roll bending and crossing of both work rolls and back-up rolls is carried out. The roll crossing is a paired-crossing type wherein a work roll and its associated back-up roll are crossed to the same degree as a pair. An "equalizer beam" is used to accomplish such paired-crossing.
Japan Patent 5-237511 shows crossing of both the work rolls and the back-up rolls in a 4-high rolling mill. Angles of crossing are controlled so that axial thrust force resulting from contact of the work roll with the work product is cancelled, at least in part, by thrust force in the opposite direction resulting from contact of the work roll with the back-up roll.
U.S. Pat. No. 5,365,764 describes a 2-high rolling mill using solely work roll crossing to perform strip crown control.
U.S. Pat. No. 5,666,837 describes a 4-high rolling mill using crossing of both work rolls and back-up roll in combination with roll bending. It teaches use of a lubricant in the nip between each work roll and back-up roll to reduce axial thrust force in the mill.
U.S. Pat. No. 5,765,422 describes a 4-high rolling mill wherein crossing of both the work rolls and back-up rolls is carried out with use of at least one motion transmission mechanism for cross displacement of the rolls.
U.S. Pat. No. 5,839,313 describes crossing of solely intermediate rolls in a 6-high or 5-high rolling mill to eliminate the disadvantages of work roll crossing.